Cleon
Legend
Arms. Melee Weapon Attack: +5 to hit, reach 10 ft. [?], one target. Hit: 10 (2d4 + 5) [?] bludgeoning damage, and the target is grappled (escape DC 17). Until this grapple ends, the creature is restrained, and the sea star can't grapple another target.
Engulf #1. Melee Weapon Attack: +5 to hit but target must be restrained, with Advantage against creatures with rigid shells (giant crabs and insects, humanoids in plate or banded armor, etc.), reach 5 ft., one restrained target. Hit: 10 (2d4 + 5) bludgeoning damage [?] plus 7 (2d6) acid damage [?]. Once an Engulf hits, if the sea star misses with a subsequent Engulf attack it still does 7 (2d6) acid damage [?] to the target as long as the target is restrained.
Maybe increase the acid damage and lower the bludgeoning damage?
I'm wondering whether the arms might do the same base dice as a Brittle Star since it's basically similar, just with a higher Strength bonus.
Arms #2. Melee Weapon Attack: +5 to hit, reach 10 ft. [?], one target. Hit: 7 (1d4 + 5) [?] bludgeoning damage, and the target is grappled (escape DC 17). Until this grapple ends, the creature is restrained, and the sea star can't grapple another target.
Engulf #3. Melee Weapon Attack: +5 to hit but target must be restrained, with Advantage against creatures with rigid shells (giant crabs and insects, humanoids in plate or banded armor, etc.), reach 5 ft., one restrained target. Hit: 7 (1d4 + 5) bludgeoning damage [?] plus 10 (3d6) acid damage [?]. Once an Engulf hits, if the sea star misses with a subsequent Engulf attack it still does 7 (2d6) acid damage [?] to the target as long as the target is restrained.
That's still Challenge 1 according to the CR calculator.
Hmm… I still prefer the Arms #1 & Engulf #1. A sea star is crushing / prying at its prey with its whole body and arms, it's not just grabbing it with one arm like our brittle star does. It presumably usually Multiattacks the same target with two arms (2d4+4) and a bite, so its arms do similar damage to a sea star with a single 2d4+5 Arms attack.
Playing around with the CR calculator, it appears to be quite close to the top of CR 1. It only takes a single point of more damage to bump it into CR 2.
Maybe we should make it Challenge 2 with a bit higher damage and the normal base 10 on its to hit?
Arms #3. Melee Weapon Attack: +7 to hit, reach 10 ft. [?], one target. Hit: 10 (2d4 + 5) [?] bludgeoning damage, and the target is grappled (escape DC 17). Until this grapple ends, the creature is restrained, and the sea star can't grapple another target.
Engulf #4. Melee Weapon Attack: +7 to hit but target must be restrained, with Advantage against creatures with rigid shells (giant crabs and insects, humanoids in plate or banded armor, etc.), reach 5 ft., one restrained target. Hit: 10 (2d4 + 5) bludgeoning damage [?] plus 10 (3d6) acid damage [?]. Once an Engulf hits, if the sea star misses with a subsequent Engulf attack it still does 10 (3d6) acid damage [?] to the target as long as the target is restrained.
Alternatively, we could keep the previous Arms #1 & Engulf #1 and make it Challenge 2 by increasing the Hit Dice. A Sea Star is a good deal more robust than a Brittle Star after all, which is, well, brittle.
We could give it, say Hit Points 59 (7d10 + 21) or 68 (8d10 + 24) or increase the CON to 18 (+4) for Hit Points 57 (6d10 + 28) or 66 (7d10 + 28) and it comes out CR 2.
What do you reckon.